Since salivary glands and their secretions play an essential role in maintaining the oral environment, information on the development and differentiation of the secretory units may lead to a better understanding of the functional aspects of these organs in health and disease. Normal activity of salivary glands is controlled by neural stimulation and recent studies on rodents suggest that experimental stimulation with synthetic catecholamines, especially isoproterenol (ISP), leads to alteration of salivary gland structure and function. This study is proposed to determine the role of the Beta-adrenergic activity, elicited by ISP, on the morphological development and biochemical differentiation of the major salivary glands, and therefore, demonstrate a neural control mechanism in their development. ISP treatment of postnatal rats will begin prior to the period in which the salivary glands show the greatest amount of development. The effects of the Beta-adrenergic antagonists propranolol will also be studies after treatments comparable to those of ISP. Morphological development of the parotid, submandibular, and sublingual will be determined by electron microscopic studies and biochemical differentiation will be determined by monitoring changes in protein patterns in the glands by acrylamide gel electrophoresis. It is anticipated that excessive Beta-adrenergic stimulation by ISP will induce exaggerated changes in the glands representative of discrete cellular changes which progress more slowly in normal development. Inhibition of normal development by propranolol will strengthen the supposition that Beta-adrenergic stimulation plays an important role in controlling development of the major salivary glands.